For implementing real three-dimensional floating images, a passive optics has been developed using nanofabrication technologies that finely divide a light beam; this passive optics allows a mirror image to be formed as a real image in space (see the nonpatent document 1 described later).
Many fine openings are formed through the substrate of the optics. Each of the fine openings is 100×100×100 μm. Two adjacent interior surfaces of each opening serve as a micromirror. That is, two adjacent interior surfaces of each opening are used as a dihedral corner reflector. Light passes through each opening while being reflected by the micromirror at two times so that a mirror image is formed.